A waste of space: Bulk of drive capacity still underutilized

Slumberland Furniture, a Little Canada, Minn.-based company with 2,300 employees and two data centers, was an early adopter of thin provisioning technology. Seth Mitchell, an infrastructure team manager at Slumberland, said the company began using storage arrays from Compellent with thin provisioning in 2004. The company's main SAN has 62.4TB raw capacity, and the other has 8TB.

Because of online retail sales and financial records requirements, the company has intense I/O needs, so 62.5% of the primary storage resides on high-performance Fibre Channel disk, with the remaining capacity on Serial ATA (SATA) disk.

Currently, the company has a disk capacity utilization rate of 66%. Mitchell estimated that if he were not using thin provisioning, the capacity utilization rate would hover around 30%.

Slumberland didn't choose Compellent solely because of its array's default thin provisioning capability. The company needed it more for its modular design, which allows it to grow in capacity and performance over time.

"We have an environment like many retailers, where you really need to prove everything with numbers one step at a time and start small. With a lot of vendors, you had to start with a larger system, or other vendors had smaller systems that required you to rip and replace when you wanted a larger model," Mitchell said.

Over time, however, Slumberland began using Compellent's automated information life-cycle management feature, which places less used or less I/O-intensive data on lower-cost SATA disk or on tape-based policies.

Compellent's technology works by alerting a systems administrator that a capacity threshold is being reached by an application server. The admin can then allocate more capacity with the click of a button.

In comparison, Texas Christian University in Fort Worth, Texas, rolled out its first SAN with thin provisioning from 3Par only two years ago. Prior to that, the company relied on DAS.

Bryan Lucas, executive director of technology resources at the university, said the school has also been implementing a server virtualization strategy that has helped with storage provisioning and easier management requirements.

To date, Texas Christian has virtualized 30% of its 350 servers, with a goal of eventually virtualizing 80%. The school is adding about five servers per month, and virtualization will help cull the number of physical servers needed.

Prior to implementing server virtualization and SANs, the school literally had rack upon rack of DL380 and DL460 servers, with spare disk capacity on all of them. "We just don't have that today. We have racks of blades and pools of SAN drives," Lucas said.

Like other IT managers, Lucas found DAS easy to deploy and manage -- until the school's server farm began to grow. Then managing the disparate DAS islands became unwieldy and inefficient.

"As power became more of a concern, as was physical space, the direct-attached model didn't scale well," he said. "The problem we ran into is having spare capacity on a box. We're buying that server and disk drives thinking it needs to last three or four years, and two or three years later we're buying more. Thin provisioning solves that problem by default. We've been really pleased with the result."

Lucas said his staff doesn't include a SAN specialist, but managing the network has been relatively easy. Since deploying 3Par SANs, he has reclaimed between 40% and 50% of his disk capacity and reduced power consumption by 10% to 20%.

"You don't have all these extra drives spinning that you're not making use of," he said.

Lucas installed the first 3Par InServ S400 array in early 2008, putting the school's generic file server traffic on it, quickly followed by the school's student e-mail system.

He said the school now has three SANs. Thin provisioning is being used on two. The third SAN is mainly in support of video streaming, which would not benefit greatly from thin provisioning.

Lucas said he was cautious about deploying a SAN at first, believing he would need additional staff to manage it. But his vendor has provided proactive support, and the system has run smoothly without needing any regular tweaks.

"I'm not having to dedicate an [an employee full time] to manage the storage infrastructure. It's just much easier than I expected," he said. "We've been through two years of this, and I'm still not looking around saying, 'I need to hire additional staff to manage this.' "

Reclaiming storage

One other way leading storage vendors have attempted to address poor utilization rates is storage reclamation. Leading storage vendors, such as EMC, Hitachi Data Systems, IBM and Symantec, have come out with storage reclamation algorithms in their management software, which identifies unused data blocks, marks them and then places them back into a pool of available storage.

Symantec's Storage Foundation software suite uses an API to enable automated storage reclamation across storage hardware from several major vendors, including Microsoft Hyper-V virtual storage environments.

The T10 Technical Committee of the International Committee for Information Technology Standards is working to make the API a standard for the rest of the industry that would allow storage management software from various vendors to automatically mark and reclaim unused blocks of data capacity.

"What we've seen over the past two years is an increased focus on sharpening the pencils and utilizing the data storage assets companies have in order to eke out better utilization rates," Loftgren said.

"And we see a lot of interest in that and technologies that are going to help companies lower their overall costs."

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Lucas Mearian

Computerworld (US)
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